DAC mode voltage tests

Post-installation and operation tests on cable lines have become a requirement imposed by power companies on installers to enhance energy flow safety. Voltage tests are mandatory for cable systems above 1 kV, while it is allowed not to perform them for lower value ranges. Currently, numerous lines have been modernised or new connections are created to integrate energy sources with the designed infrastructure. Thus it has become necessary to run voltage tests and a number of other diagnostic activities as well as low- and high-current tests. GK-Elektro conducts DAC mode voltage tests on 110 kV high-voltage lines plus develops documentation necessary to commission the lines.

DAC measurements – specification

The diagnostic services provided by our company conform to International Electrotechnical Commission’s standards. Among others, they specify test methods and requirements for 6 kV – 150 kV cabling. Additionally, Commission’s standards define testing schemes and methods. As per their recommendations, a DAC oscillating voltage test should be performed in the form of “shots” (voltage releases) within the limits of 200 Hz and 5 kHz, in addition to which 50 releases per phase should be triggered to test the cable voltage range.
Apart from the International Electrotechnical Commission, similar requirements are defined by other institutions and documents which unanimously define the number of releases, but differ, e.g. in terms of test voltage frequency or value. Thus other power companies can also define applicable guidelines, i.e. they can set up voltage tests based on their own experience and guidelines, however, still ensuring conformance to generally accepted standards and documents.

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Voltage testing methods

DAC mode voltage tests constitute one of numerous power line testing methods. All acceptance testing is conducted using two methods, i.e. a high-voltage and low-voltage methods. The latter is often employed by competent contractors already equipped with necessary meters, load emulators or other current flow testing gear. High-voltage testing is a more complicated form of measurement requiring cutting-edge equipment and power generators. Such equipment must be transported in vans and its installation can take several hours. High-voltage measurements include AC, PD and DAC tests. Systems based on the DAC method utilise voltage tests with parameters different from other tests, and ensure conformance with the above-mentioned International Electrotechnical Commission’s standard, i.e. IEC 60270.

Solutions offered by DAC mode voltage tests

Cables subjected to a voltage test may either withstand the examination or fail, which will force the installation company to take additional steps. To pass this test, cables must withstand, e.g. the energy flow from a generator for a certain period of time, usually about one hour. With the voltage test performed, a correct installation method may also be determined. Cable installation errors constitute certain causes of failures that may not be detectable at the test level, but may occur during operation. For this reason, correct installation of cable accessories, cable boxes and terminals is essential to gain acceptance of cables for use, and results from diagnostic work performed.

DAC mode voltage tests and technical condition assessment

Electromagnetic transmission cables need to be carefully inspected for their technical condition. Detection of any irregularities within the entire system or its individual components is particularly important in failure risk mitigation processes. Thus testing both the voltage and cable installation quality becomes key. DAC diagnostics can be employed on new cables and lines that are already in service, which makes factory testing, as well as periodical or preventive testing, essential. DAC mode voltage tests and cable line tests facilitate defect and exposure elimination and make it possible to determine the technical condition or even the life span of a cable network.

DAC voltage test – characteristics

Damped Alternating Current (DAC) is a type of alternately damped voltage with the frequency equal to 20,500 Hz. This testing method is employed in a wide range of cable systems with medium, high and very high amperage. By generating the AC current up to a specified voltage level and then discharging it, a test object is subjected to diagnostic tests and measurements. DAC testing offers a state-of-the-art tool suitable to maintain or monitor high-voltage cabling.
DAC mode voltage testing is a cutting-edge solution used since 1999. This method was first presented during the Jicable Conference held in Paris, and ever since it has been the main and most effective voltage measurement method used in the electric engineering industry. GK-Elektro specialises in providing electric system-related services and its offering includes such tests and measurements. Contact us for details of our offering or to order a particular service.